1. Field of the Invention
The present invention relates to a connector. In particular, it relates to a connector that can achieve fine pitches and low contact resistance with a simple construction, and an electronic component provided with this connector.
2. Description of Related Art
Heretofore, techniques have been investigated by which an IC package, such as a CPU, an LSI, or the like is mounted on a printed circuit board via a socket, and a socket for installing, a CPU, such as an LGA package, a BGA package, or the like, is mounted on many mother boards of personal computers and servers. There has been yearly progress in the number of pins and speed of CPUs owing to improvements in their functions and performance, and corresponding measures have been taken by increasing the size of the packages and making them more finely pitched. Accompanying this, sockets are required that can deal with the number of pins, and at the same time deal with the increase in the amount of bending accompanying the size increase of the packages, and that can deal with the dispersion of the heights of the contact loads and/or the solder balls of the packages. Therefore, it is important to make the size of the socket contacts small, and it is desirable to ensure that the contacts between the IC pins and the sockets have an appropriate contact pressure. Furthermore, it is important that the contacts have low inductance at high speeds, and it is required that the contact resistance is low, and the allowable current is high, corresponding to the increase in current consumption due to the high speeds.
Mainstream sockets for current LGA packages have 400 to 800 pins with a pitch of approximately 1 mm. For example, as described in Patent Document 1 and Patent Document 2, a construction is used that is manufactured by folding a metal plate in a complex way in order to form a predetermined contact shape, and inserting the contact in a socket housing.
Such a method is a system in which an appropriate load is generated at a predetermined stroke by making the metal contact function as a spring in order to obtain a stable contact resistance. Moreover, in the process for obtaining a predetermined contact pressure, when the load is increased, the contact location is shifted so that a wiping effect can be expected whereby oxide film and/or contamination on the surface can be removed.
However, fine pitches are difficult to be achieved using these methods. When trying to achieve a fine pitch, it is necessary to shorten the length of the cantilevered part of the spring of a contact terminal. However, if the length of the spring is shortened, in the case of a cantilever spring with the same material and the same shape, the load required to obtain a predetermined stroke increases. Therefore, if the wire diameter (width and/or thickness) of the cantilever spring is reduced in order to generate the appropriate load, the permissible stress is required to be low, so in spite of the original intention of moving it in the elastic deformation zone, it undergoes plastic deformation, making it impossible to withstand a predetermined load. This is because the permissible stress is proportional to the wire diameter (width and/or thickness) of the spring, while the spring constant, which is the main factor for determining the load, is proportional to fourth power of the wire diameter (width and/or thickness) of the cantilever spring.
Considering this, instead of the method of obtaining a predetermined contact pressure due to the load of a cantilever spring, a technique has been devised in which the metal of the contact part is designed in a region where it undergoes plastic deformation, and the repulsion force is compensated by rubber or an elastomer. For example, in Patent Document 3, the function of the contact part is realized by flexible printed circuit boards, and a construction is disclosed in which the elastomer is sandwiched between two flexible printed circuit boards, and the flexible printed circuit boards are joined by soldering metal pins provided separately in order to obtain top to bottom interlayer conduction.
In this technique, metal domes are formed at the parts in contact with the flexible printed circuit boards, and the metal domes make contact with the facing contact points. Furthermore, if the load is increased in a process for obtaining a predetermined contact pressure, the contact locations shift, so that a wiping effect for removing oxide film and/or contamination from the surface can be expected.
Moreover, in Patent Document 4, a method is disclosed in which metal plating is applied to an elastomer in which predetermined dome shapes and through holes have been formed in advance by a metal mold, and a circuit is formed using a photolithographic process such that contacts are connected by the through holes and the domes.
However, as disclosed in Patent Document 3, the method in which the flexible printed circuit board is sandwiched by an elastomer requires a process for manufacturing two flexible printed circuit boards on which circuits are formed in required patterns, and furthermore, it requires metal contacts for obtaining interlayer conduction to connect them. Therefore, the number of parts is large, which makes it difficult to achieve miniaturization. Moreover, since a process is required for connecting the flexible printed circuit boards and the metal pins, there is a problem in that the manufacturing method becomes complex. Furthermore, as disclosed in Patent Document 4, there are still many areas for development in techniques for plating on elastomers, and there is a problem in that mass-production techniques have not been established in general. Moreover, in Patent Document 4, since contact pressure is obtained by the dome parts being deformed, the contact locations do not change, so that there is also a problem in that a wiping effect cannot be expected.    [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2004-158430    [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2005-019284    [Patent Document 3] Japanese Unexamined Patent Application, First Publication No. 2004-071347    [Patent Document 4] Japanese Unexamined Patent Application, First Publication No. 2001-332321